Receiving system



LSZLSQ Dec, 30, 1

D. G. M CAA RECEIVING SYSTEM Filed Nov. 17, 1922 4 Snvwntoz W Q9 MPatented Dec. 3(1 1924.

ire sTA'rEs PAE OFFIGE.

DAVID G. MGCAA, 0E LANCASTER, PENNSYLVANIA, ASSIGNOR TO THE ELECTRIC AP-PARATUS 00., OF PARKESBURG, PENNSYLVANIA, A CORPORATION OF PENNSYL-VANIA.

RECEIVING SYSTEM.

Application filed November 17, 1922. Serial No. 601,455.

To all whom it may concern:

Be it known that I, DAVID G. MGCAA, a citizen of'the United States,residing in Lancaster, county of Lancaster, State of Pennsylvania, haveinvented new and useful Improvements in Receiving Systems, of which thefollowing is a specification.

My invention relates to a method of and apparatus for'eliminating orreducing the effects of electrical disturbances in the reception ofsignals, telegraphic, telephonic or otherwise, represented byalternating current, and particularly alternating current o r\oscillations of radio frequency.

In accordance with my invention, the effects of static, atmospherics,strays and other natural or artificial disturbances including otherradio signals, are reduced or eliminated in a radio or other receivingsystem, whereby the desired signals are readily distinguishable orbecome intelligible notwithstanding the simultaneous existence of strongdisturbing effects.

In accordance with my invention, the received energies representing boththe desired signal and the disturbing effect are divided into pathsincluding reactive devices, one of which is employed for effecting thetranslation of the desired signals, and with another of which isassociated a local source of alternating current or'oscillations in suchwise as to cause the effect of said other reactance to fluctuate withinwide limits and thereby causing the signal-representing energy in thefirst reactance to fluctuate in amplitude and at certain instants to bereinforced by energy from the local source, to the substantial exclusionor great reduction of the effects of the simultaneously existingdisturbing energy. v

In accordance with my invention, the aforesaid current locally producedhas a frequency which preferably is different from the frequency of theenergy representing the desired signal, though it may be of the samefrequency as hereinafter described, and in either or both cases it ispreferred that the locally produced energy in its reaction with theoscillations representing the desired signal and the disturbing effectsshall be substantially equal to the amplitude of the oscillations of thedesired signal, whereby the ratio of the effect upon the signaltranslating instrument of the energy representing the desired signal tothe eflect upon that in- 5 strument of the energy representing thesimultaneously existing disturbing energy is increased, as compared towhat would be the normal effects of the signal-representing energy andthe disturbing energy were my invention not employed.

.My invention resides in the method and apparatus hereinafter describedand claimed.

For an understanding of my method and for an illustration of some of themany 55 forms my apparatus may take, reference is to be had to theaccompanying drawing, in which:

Fig. '1 is a diagrammatic view of circuit arrangements embodying myinvention.

Fig. 2 is a fragmentary diagrammatic view illustrating a modification.

Fig. 3 is a diagrammatic view of a modification where the correctivecircuit or device is applied in a secondary circuit.

Fig. 4 is a diagrammatic view of a modilied system wherein my correctivedevice 1s in effect in series with the receiver coil.

Fig. 5 is a diagrammatic view of a system involving my corrective devicein a modified arrangement.

Referring to Fig. 1, A represents the autenna or other absorptionstructure of a radio or any other receiving system, connected throughthe variable inductance L and the primary I of an oscillationtransformer to earth or other counter-capacity E, the variable condenserC serving to tune the antenna path and the circuit including the primaryI to the frequency of the oscillations pro- 99 duced in the antennasystem by the energy absorbed from the natural or other medium.Inductively related to the primary P is the secondary S of anoscillation transformer whose circuit, particularly for long wavereception, may include the adjustable inductance L For tuning thesecondary circuit, there is provided the usual tuning condenser C whoseterminals are connected to the grid circuit of the audion or othervacuum tube detector-amplifier V comprising the filament or cathode f,grid 9, and anode or plate a.

In the grid path may be connected the condenser C shunted by the leakresistance 7'. In the anode circuit of the tube V is the source ofcurrent or battery 18 and a winding T, which may be the winding of atelephone receiver, or may be the primary of a transformer deliveringthe plate circuit current or a component thereof to one or more stagesof radio or audio frequency amplifying devices, as well understoodin theart, the condenser C and theresistance 1' being omitted when theamplification is to occur at radio frequency. In shunt to the winding Tmay be connected the condenser C when the winding T is that of atelephone or the primary of an audio frequency transformer, thecondenser G being omitted in the case where the winding T is the primaryof a radio frequency transformer, all as well understood in the art.

As thus far described, the receiving apparatus is a usual one and per seis not my invention.

However, in accordance with my invention, there is connected in parallelwith the primary P, or in any other divided or snuably related path orposition therewith as regards the antenna circuit or other pathtraversed by the oscillations of the desired signal and thesimultaneously existing dlsturbing effect, a reactance, eithercapacitative or inductive, but preferably, as shown,

, an inductive reactance L whose amount may be adjustable as indicated.It is preferred that the resistance of the inductance L shall be smallas compared with its inductance. The magnitude of the inductance L ispreferably so chosen that its reactive effect is great compared withthat of the primary P for oscillations of the frequency correspondingwith that of the desired signal.

whereby, if the reactances L and P only were present, the oscillationsrepresenting the desired signal attain a far. greater magnitude in theprimary P than in the inductance L However, the reactance or inductanceL i by itself is insufficient for my purposes, and

there is connected in series therewith a variable condenser G which maybe connected as indicated, and preferably. to the terminals ofadditional inductance in series with the inductance L this additionalseries in-- ductance being indicated at L and may be in effect acontinuation of the inductanc:

L and forming therewith in effect an autotransformer. For a givenfrequency of the oscillations representing the desired signal, thecapacity of the condenser C. may be adjusted to a value 'with respect tothe magnitude .of L -L which causes the reactance of the" path L C, L inshunt to inductance L for that; fre-' quency to Vanish or become zero orsub stantially zero, whereby, under suelrcondition and for such time,the effect is the same as if the reactance of inductance L? were reducedto zero because primary P is substantially completely robbed ofsignal-representin'g ener y. That is to say, this effect is.

the same as if inductance L were short circuited or as if the leads tothe two terminals of the inductance L were brought into low resistanceconductive contact with each other. The magnitude of the capacity of thecondenser G for this condition is not that which would be given to thecondenser Ctto tune the control circuit L L C by itself or whenisolated, to the frequency of the oscillations representing the desiredsignal, but has been found to be considerably greater, and for long wavelengths, as of the order of 13,000 meters, is substantially three orfour times as great. In operation of the system, this large desiredvalue of the capacity of the condenser C is found by trial by manuallyadjusting the condenser,

to produce optimum effect.

If the control circuit L L O with such large value of capacity of thecondenser C is opened, the reactance or impedance across the terminalsof the inductance L resumes 'its initial or normal value, with theresult that in the primary P the amplitude of signal-representingoscillations would again be large. 'Therefore, .by periodicallyinterrupting the circuit L L C the amplitude of signal-representingoscillations in the primary P will be alternately large andsubstantially zero.

What has been said of the oscillations representing thedesired signalisalso true of those oscillations simultaneously present in the antennasystem and due to the absorption thereby of the energy representing the"disturbing efli'ects of static, atmospherics,

L C is closed, the amplitudes of the two sets of oscillations in theprimary P are sub stantially niI. v

I With the apparatus thus far described, the effects-of static, etc.,have not been reduced or eliminated, as distinguishedvfrom the .signal-representing energy; both are absent from the receiving-"apparatusrepresented-by the prlmary P when the control circuit.

L L C is closed, though both are present in said-control circuit and theremainder of the antenna path, and both are present in the receivingapparatus when said circuit L L 0 is open. i

However, to greatly reduce the effects of static or other disturbances,there is placed in inductive relation to the control circuit 1 or to anysuitable part thereof, a one of the inductances L, a coil D,- pref andthe disturbing effects of static, etc., and

so much different therefrom that the beat is of audible frequency fortelegraphy and is of super-audible or inaudible frequency for telephony.

lVhen the frequency of the oscillations traversing the source D isequalto the frequency of the oscillations representing the desiredsignal and the interfering staticeffects, the apparatus is uti]izable\for telephony. t f

Byway of example, merely, the local source of oscillations is anoscillating audion V it being understood, however, that any,

other suitable source may be employed.

Assuming the oscillations representing the desired signal to be weak orto have small amplitude, and the interfering effects, as static, strays,etc., to be of great amplitude or relatively strong, the oscillationsrepresenting the desired signal have an amplitude which is smallcompared with the amplitude of the oscillations set up in the receivingantenna or other circuit by the atmospherics, strays, static, etc.

In order that the strong oscillations representing the disturbancesshall not maintain their relative strength in their effect upon thetelephone or other instrument T, the coil D is rotated or moved to suchposition with respect to the coil ll that the amplitude of theoscillations .induced in L by the coil D shall be substantially equal tothe amplitude of the oscillations representing the desired signal,though simultaneously there exist in the circuit L L C oscillationsrepresenting the static or other disturbances of an amplitude which isrelatively great with respect to the amplitude of the oscillations ofthe desired signal.

There accordingly occurs in the circuit L L C reaction by the weakoscillations induced in that circuit by the coil D upon the.

oscillations representingthe desired signal, and also upon theoscillations of relatively far greater amplitude representing thedisturbing efiects of static, etc. There are accordingly produced twosets of beats. The first set is the beats produced by reaction with theoscillations of small amplitude representing-the desired signal, andthese beats are full or perfect in the sense that the signal waves arenon-decadent, and, secondly,

in that the beat amplitude varies between substantially zero and twicethe amplitude of the oscillations representing the desired signal. Theother set of beats is that produced with the oscillations of relativelyfar greater amplitude and representing static, etc., and these beats areimperfect, first-in the sense that the oscillations representingstatic'are generally decadent, and secondly, because the amplitude ofthe oscillations representing static is great compared with theamplitude of the reacting oscillations induced by the coil D, with theresult that the beats whose components are the weak oscillations from Dand the strong oscillations representing static, etc., a maximumamplitude which is only relatively slightly greater than the amplitudeof the oscillations representing static, etc., while in the case of thebeats eifected by means of the oscillations of lesser amplituderepresenting the desired signal the maximum beat amplitude is abouttions from the local source D upon the amplitude of the beats caused byoscillations representing st'atic. etc. is proportionately smaller thanthe efiect upon the amplitude of the beats due to the oscillationsrepresenting the desired signal.

Accordingly, during the presence of oscillations of small amplituderepresenting the desired signal in the circuit L L, 0*, there is a timewhen the resultant of the reaction thereof with the oscillations ofequal amplitude induced by the coil D is substantially zero, and thereactance across the terminals of the inductance L is the normal onecorresponding to the conditions of opening the circuit L L C; at anotherperiod the oscillations representing the signal and induced-by the coilD are cumulative, andthere is flowing in the circuit L If, C asignal-representing current of substantially double amplitude; and underthese circumstances, the condenser C having the aforesaid capacity, thereactance between the terthe oscillations representing thedesiredsignal. When the oscillations induced by the coil- D are in oppositionto the oscillations representing the weak signal, there is a cumulativeeffect in'the primary P of the locally produced oscillations and thoserepresenting the desired signal; and vice versa, when the local andsignal oscillations are cumulative or assist each other in the circuitof the condenser they oppose each other in the primary P. That is tosay, in addition to the aforesaid fluctuations inmagnitude of effectsupon the receiving instrument, as the signal-translating instrument T,the oscillations traversing the coil Dproduce an effect upon the primaryP, and therefore upon the signal-translatmg mstrument T, cumulative withthe aforesaid sigternating current of certain magnitude is flowingtherein, the impedance across the terminals of L is small or zero, orwhen there is zero or substantially zero current in the circuit L L Cthe impedance or reactance across the terminals-of the inductance L isits normal one, as if said circuit were' open. In other words, thearrang ment and mode of operation are such tha the inductance L may besaid to exhibit normal or substantially zero-reactance, according as thecurrent in the circuit including the condenser C is zero or of finitevalue.

Assuming now that there exists simultaneously with the oscillationsrepresenting the desired signal oscillations of far greater amplituderepresenting static or the like, there is in the circuit of thecondenser C, due to the oscillations representing static or the like, abeat current which does not fall to Zero,but fluctuates between narrowlimits 1 at relatively high. amplitude. Accordingly,

as regards the beat current due to static orother effect, the impedanceor reactance across the terminals of the inductance L is small or zero,and, no more static effect reaches the primary P and signal-translatinginstrument T than corresponds with the amplitude of the oscillationinduced in the circuit of the condenser C by the coil D.

Accordingly, by choosing the amplitude of the oscillation induced in thecircuit of the condenser C by the coil D of a magnitudesubstantiallyequal to that of the oscillations representing the desired signal, theimpedance or reactance across the terminals of the inductance L is lowor zero for all of that part of theenergy representing static exceptthat part which is comparable to the amplitude of the oscillationinduced by the coil D, with the result that the eflect upon the primaryP, and therefore upon the signal-translating instrument T, of static isno greater than that of the desired signal effects. y

In other words, by the employment of the condenser C of the desiredmagnitude and its circuit, the greater portion of the rela- .tivelygreater effect due to static is withheld from the primary 1? andsignal-translating instrument T because of the then correspondingly lowor zero reactance across the terminals of the inductance L Viewing thematter in another way, there exist simultaneously in the circuit of thecondenser C oscillations .of great magnitude representing static andoscillations of relatively small magnitude representing the desiredsignal; these oscillations produce reaction with the Weak oscillationsinduced,

by the coil D resulting in heat eflects in the circuit .of the condenserCflwhich, as regards variation of amplitude of the beat effects, aresubstantially equal for both the static and signal effects, and theremaining weak signal oscillations are in oppositephase and neutralizingeach other, and a signal is therefore manifested at T, because thereactance across the terminals of the inductance L is great under suchcondition; while as regards the strong static effects, the weakoscillations induced by the coil D do not completely annul the staticoscillations in beat format-iomand therefore, as regards the staticeffects, there is always substantial current flowing in the circuit ofthe condenser C, and for such static effects, therefore, the reactanceacross the terminals of the inductance L is small or zero, and suchstrong static effects are therefore withheld from the primary P and thesignaltranslating instrument T.

When the frequency of the oscillations induced by the coil D is equal tothe frequency of the oscillations representing the Weak signal and alsothe strong static, beat effects are produced, or beats of zero frequencyare produced, the characteristic action being the same in that thepredominant effects of static cause the reactance across the terminalsof the inductance L to be zero or small, and therefore produce no effectupon the signal-translating instrument T, and only that portion of theenergy representing static produces an effect upon the instrument Twhich corresponds in amplitude with the amplitude of the oscillationsrepresenting the desired signal.

In connection with the receiving circuit proper, as the circuit of thesecondary S and its adjuncts, it will be found that when the condenser Cis adjusted to that magnitude which will attune the circuit S, L C tothe frequency of the oscillations representing the desired signal, andwith the circuit L,

' signals through static as above described,

with the circuit L L C present with the local source of oscillations inoperation. But the condenser G must be adjusted to a value of capacitygreater or less than its aforcsaidvalueto tune to the radiocomponent ofthe partial beats due to static, ac-

cording as the coilD is inducing in the cir-- cuit of the condenser Coscillations of frequency less than or greater than the frequency of theoscillations representing the desired signal. And the greater thedifference between the frequencies of the locally producedoscillations'and those representing the signal, the greater is thedifference in the settings of the condenser G as between tuning to thefrequency of the signalrepresenting oscillations and the radio com-'ponent of the static effects. In other words, by varying theadjustmentof the condenser C as aforesaid, the receiving circuit may be attunedwith respect to the signalrepresenting oscillations, and for the samesetting the circuit will be de-tuned with re spect to the radiocomponent of the static effects in the same circuit.

While in the arrangement of 1 the condenser C is in a circuit or pathconductively related to the antenna circuit'or path or directly coupledto L it may be placed in a path coupled to or inductively related to theantenna path, as indicated in Fig. 2,

'- wherein the aforesaid inductance ill 5 serves as the primary ofanoscillation transformer whose secondary is an mductance L, H]. circuitwith which isthe aforesaid condenser as before, in the case of Fig. 1,when the cir- (3*, and in inductive relation to the circuit L, C isdisposed the aforesaid coil D tra.v

ersed by the locally produced oscillations. in this case the magnitudesof inductance l. and capacity C are such as to tune to the frequency ofthe oscillations representing the desired signal when coupled to L but,

. cuit L C is isolated, a smaller value of capacity C will serve to tuneto the frequency of the oscillations representing the desired signal.

As indicated in Fig 3, the primary P and the inductanceiL correlated inthe manner indicated in Fig. 1 or 2, are disposed not directly in theantenna path, but in a secondary circuit comprising the secondary Sinductively related to the primary P in the antenna path, the S beingtuned by the variable condenser C and, if suitable or desirable, by theinductance L. r

Referring to FigzA, there is shown an arrangement wherein, in effect,the corrective or control circuit is serially related to the receivercoil or primary P. In this instance the inductance L of-the controlcirtance L and primary circuit of the-secondary cuit or correctivedevice is in series with the receiver .prnnary P, whether directly inthe antenna circuit, asindicated, or in a seconprimary P.

In action, the closecoupling between the coils L and L causes largetransfer of energy to the circuit L C during thoseltimes that it iseffectively closed by the efiect of the locally produced oscillationstraversing the coil D. On the other hand, the loose coupling between Pand S permits suitable amount of signal energy to be transferred. from P'to the secondary circuit S at those times when the circuit L 0 is ineffect open. When the circuit L O is in effect open, that is, when theimpedance L has its normal or'maxi'mum eflect, L and P, to-

locally produced oscillations of getherwith the condenser C, attune theantenna circuit or other path to the frequency of the received energy.While herein the condenser C is shown as in series with the which issuitable particularly antenna path,

it will be understood that for short waves,

it may be connected in parallel to the induc- P for long wave reception.

Referring to Fig. 5, the secondary receiving circuit is, as before,associated with the primary P, with which-is associated in turn acircuit L L C as in Fig.1. In circuit with theprimary P is a furtherprimary P of an oscillation transformer whose secon dary S is in thegrid circuit of a thermionic or audion amplifier V in whose anode orplate circuit is the coil D in inductive relation with the circuitcontaining the 0011- denser G which is adjusted to the capacitymagnitude discussed in connection with Figsl.

' lhe primary P when traversed by feeble signalsrepresentingoscillations, inductively affects the grid circuit of the amplifier Vwhich in turn causes an amplified signalrepresenting"oscillationtraversing the coil D which inductively affects the circuit containingthe condenser 0 with the result that when signal-representingoscillations traverse the primaries P, P*, thereactance of theinductance 1L attains its normal or high value, forcing moresignal-representing current through the primaries P, P*, and the actionis again built up through the coil D cillations possible.

in its efi'ect upon the circuit of the condenser C until finally thesignal effects in P are increased to a maximum, due to the fact that thereactance of the inductance L has attained a maximum." In this case, thecoil D is traversed by oscillations of signal frequency, and not of afrequencyv diflering from that of the signal frequency or a frequencyrepresenting the static or other disturbance, and the circuitarrangement is utilizable for telephony. Tn shunt to the secondary 8*may be connected the tuning condenser C for tuning the grid circuit forenhancing the efiects described.

, By the arrangement of Fig. 5, signal-rep resenting oscillationspassing through the primary P are utilized in amplified form forinfluencing the circuit containing the condenser C to eflect suchcurrent strength therein as to in effect open that circuit, as by theincrease of reactance of the inductanee L accordingly forcing moreof thereceived signal energy through the primary P, Here again the reaction ofthe signal frequency oscillations with the strong osrepresenting therelatively stronger static or other disturbing effect produces theresult hereinbefore described in connection with Fig. 1, in that thereis an increase in the ratio of the magnitude of the effect in thetelephone or other translating instrument T of the'oscillati'onsrepresenting the desired signal to the magnitude of the effect producedupon the instrument T by the static or other disturbing effect.

While in the foregoing description currents of radio frequency have beenassumed and considered, it will be understood that my invention is notlimited thereto, but in its broader aspect comprises a method of andapparatus for differentiating between currents, whether of audio orradio frequency, which may be of the same frequency 'but of differentamplitudes; or comprises a method of and apparatus for reducing thedlfi'erence between effects of'such .audio or radio frequency currents,whereby the weaker may produce a desired effect of:

greater relative magnitude than otherwise What I claim is: \i 1. Themethod of distinguishing between I fluctuating currents of, diflerentamplitudes,

which comprises impressing the currents upon a current-translatingcircuit and upon a control path upon the magnitude of whose reactancedepends the magnitude of effect in said translating circuit, andrendering said'reactance of small magnitude for withholding from saidtranslating circuit effects of said current of greater am litude.

2. The method of distingulshing between fluctuating currents of the samefrequency but different amplitudes, which comprises impressing thecurrents upon a eurrenttranslating circuit and upon a control path uponthe magnitude of Whose reactance depends the magnitude of effect in saidtranslating circuit, and rendering said reactance periodically of smallmagnitude for Withholding from said translating circuit effects of saidcurrent of greater amplitude.

3. The method of distinguishing between fluctuating currents ofdifferent amplitudes, which comprises impressing the currents upon acurrent-translating circuit and upon; a control circuit includinginductive and capacitative reactances, and impressing upon said controlcircuit a fluctuating current for rendering its reactance periodicallyof reduced magnitude for withholding from said translating circuiteffects of the current of greater magnitude.

4. The method of distinguishing between fluctuating currents of the samefrequency but difi'erent amplitudes, which comprises impressing thecurrents upon a currenttranslating circuit and upon a control circuitincluding inductive and. capacitative reactances, and impressing uponsaid control circuit a fluctuating current for rendering its reactanceperiodically of reduced magnitude for withholding from said translatingI desired signal and oscillations of the same.

frequency-but of greater amplitude representing a disturbing effect,which comprises impressing both sets of oscillations upon aslgnal-translatmg circuit and a control 011- cu1t including inductlveand capacitative reactances and adapted upon reduction of magnitude ofits reactance to withhold en erg from said signal-translating circuit,an impressing upon said control circuit a' periodic current of differentfrequency.

7. The method of distinguishing between I radio frequency oscillationsrepresenting adesired signal and oscillations of the same frequency butof greater amplitude repre. senting a disturbing effect, which comprisesimpressing both sets of oscillations "upon a signal-translating circuitand a control circuit including inductive and capacitative reactaneesand adapted upon reduction of magnitude of its reactance to withholdenrent-translating means,

ergy from said signal-translating circuit, and impressing upon saidcontrol circuit a periodic current." I

8..Apparatus for distinguishing between fluctuating currents ofdifierent amplitudes, comprising a winding and. associated curareactance related to said winding for withholding energy therefrom uponreduction of said reactance, a reactance of different type associatedwith said reactance for effecting reduction of said first namedreactance to small value when said reactances are traversed bysubstantial current, means for impressing the currents of differentmagnitudes upon said winding and upon said first named reactance, andmeans for impressing upon said reactances a periodic current.

,9. Apparatus'for distinguishing between fluctuating currents of thesame frequency but different amplitudes, comprising a winding andassociated current-translating means, an inductive reactance related tosaid winding for withholding energytherefrom upon reduction of saidreactance, a .capacitative reactance associated with said inductivereactance for effecting reduction of said inductive reactance to smallvalue when'said reactances are traversed by substantial current, meansfor impressing the currents of different magnitudes upon said windingandsaid inductive reactance, and means for impressing upon said reactancesa periodic current:

10. Apparatus fluctuating currents of the same frequency but differentamplitudes, comprising a winding and associated current-translatingmeans, an inductive reactance related to said winding for withholdingenergy therefrom upon reduction of said reactance, a capacitativereactance associated with said inductive reactance for effectingreduction of said inductive reactance to small value when saidreactances are traversed by substantial current, means for impressingthe currents of different magnitudes upon said winding and saidinductive reactance, and means for impressing upon said reactances aperiodic our rent of different frequency. r

11." Radio receiving apparatus for distinguishing between oscillationsof radio frequency representing a desired signal and oscillations of thesame frequency but greater amplitude representing a disturbing effect.coniprimfng a winding, signaltranslating means associated therewith, an.inductive reactance related to said winding .for withholding energytherefrom upon reduction of said reactance, a capacitative reactanceassociated with. said inductive reactance for effecting reduction ofsaid in-. ductive reactance to small value when said reactances aretraversed by substantial current, means for impressing the oscillationsfor distinguishing between comprising a winding of different amplitudesupon said winding and said inductive reactance, and means for impressinguponsaid reactances a periodic current.

12. Radio receiving apparatus for distinguishing between oscillations ofra'dio frequency representing a desired signal and oscillations of thesame frequency but greater amplitude representing a disturbing effect,comprising a winding, signaltranslating means associated therewith, aninductive reactance related to said winding for withholding energytherefrom upon reduction of said reactance, a capacitative reactanceassociated with said inductive reactance for effecting reduction of saidinductive reactance to small value when said reactances are traversed bysubstantial cur rent, means for impressing the oscillations of differentamplitudes upon said winding and said inductive reactance, and means forimpressing upon said reactances a periodic current of a frequencydifferent from the frequency of said oscillations.

13. Radio receiving apparatus. for distinguishing between oscillationsof radio frequency representing a desired signal and oscillations of thesame frequency, but greater amplitude representing 'ing effect,comprising a winding, signaltranslating means associated therewith, aninductive reactance related to said win ding for withholdingenergytherefrom upon reduction of said reactance, a capacitativereactance associated with said. inductive reactance for effectingreduction of said inductive reactance to small value when saidreactances are traversed by substantial current, means for impressingthe oscillations of difierent amplitudes upon said winding and saidinductive reactance, and means for impressing upon said reactances aperiodic current of a frequency differing from the frequency of saidoscillations by an amount offecting beats of inaudible frequency.

' 14:. Apparatus for distinguishing between fluctuating currents ofdifferent amplitudes,

and associated current-translating means; a reactance related to saidwinding for withholding energy therefrom upon reduction of saidreactance, a reactance of different type associated. with said reactancefor effecting reduction of said first named reactance to small valuewhen said l'eactances are traversed by substantial current, means forimpressing the currents of different magnitudes upon said winding andupon said first named reactance, means for impressing upon saidreactances a periodic current, and means for adjusting the magnitude ofsaid periodic current.

15. Apparatus for distinguishing between fluctuating currents ofdifferent amplitudes, comprising a winding and associatedcurrent-translating means, a reactance'related a disturbl ili lilt lint

to said winding for withholding energy therefrom upon reduction of saidreactance, a reactance of different type associated with said reactancefor efiecting reduction of said first named reactance to small valuewhen said reac tances are traversed by substantial current, means forimpressing the currents of different magnitudes upon said winding andupon said first named reactance, means for impressing upon saidreactances a periodic current, and means for adjusting the magnitude ofsaid periodic current to an amplitude corresponding substantially withthe amplitude of the weaker of said currents. y

16. The method of distinguishing be- T tween fluctuating currents ofdifferent amof said currents.

17. The methodof distinguishing between fluctuating currents of the samefrequency but different amplitudes, which comprises impressing thecurrents upon a currenttranslating circuit and upon a control path uponthe magnitude of Whose reactance depends the magnitude of effect in saidtranslating circuit, and impressing on the control path a fluctuatingelectro-motive-force for periodically changing' the magnitude of saidreactance for periodically withholding to diflerent degrees from saidtranslating circuit the effects of said currents of differentamplitudes.

18. The method of distinguishing between fiuctu ating currents ofdifferent amplitudes, which comprises impressing the currents upon acurrent-translating circuit and upon a control circuit includinginductive and capacitative reactances, and impressing upon said controlcircuit a fluctuating current for periodically changing its reactancefor periodically withholding to different degrees from said translatingcircuit the effects of said current of different amplitudes.

19. The method of distinguishing between fluctuating current of the samefrequency but different amplitudes, which comprises impressing thecurrents upon a currenttranslating circuit and upon a controlcircuit'including inductive and capacitative reactances, and impressingupon said control circuit a fluctuating current of different frequencyjfor periodically changing its reactance for periodically withholding todifferent degrees from said translating circuit trol path forperiodically withholding to different degrees from saidsignalstranslating circuit the effects of both sets of saidoscillations.

21. The method of distinguishing between radio frequency oscillationsrepresenting a desired signal and oscillations of the same frequency butof greater amplitude representing a disturbing effect, which com-vprises subjecting to the influence of both sets of oscillations asignal-translating circuit and a control path including inductive andcapacitative reactances, and impressing upon said control path aperiodic current of different frequency for periodically varying thereactance of said control path for fects of both sets of saidoscillations. I

22. The method of distinguishing between' sustained radio frequencyoscillations representing a desired signal and decadent oscillations ofthe same frequency repreperiodically withholding to different degreesfrom said signal-translating circuit theef senting a disturbing 'efiect,which comprises" influencing by both sets of oscillations asignal-translating circuit and a control path including inductiveandcapacitative reactances, and impressing upon said control path acurrent of different frequency for periodi cally'varying the reactanceof said control path for periodically withholding to different degreesfrom said signal-translating circuit the efiects 6f both sets of saidoscillations. v

23. The method of distinguishing between radio frequency oscillationsrepre-' senting a desired signal and oscillations of the same frequencybut of different ampli-j tnde, which comprises subjecting to theinfluence of both sets of oscillations a signaltranslating circuit and acontrol path in eluding-inductive and capacitative reactances, andimpressing upon said control path a periodic current for varying thereactance of said control path for withholding to different degrees fromsaid signal-translating circuit the effects of both sets ofoscillations.

24. The method of distinguishing between radio frequencyv oscillationsrepresenting a desired signal and oscillations of the same frequencybutof different amplitude, which comprises subjecting to the influenceof both sets of oscillations a signaltranslating circuit and a controlpath inof said control path for Withholding to diffrom saidsignal-translating ferent degrees circuit the effects of both sets ofoscillations, and varying the amplitude of said impressed current to amagnitude more closely approaching the amplitude of the oscillations ofone of said sets than the amplitude of the oscillations of another ofsaid sets.

25. The method of distinguishing between sustained radio frequencyoscillations representing a desired signal and decadent oscillations ofthe same frequency representing a disturbing effect, whichcomprisessubjecting to the influence of both sets of oscillations asignal-translating circuit and a control path including inductive andcapacitative reactances, impressing upon said control path a periodiccurrent of different frequency for periodically varying the reactance ofsaid control path for periodically Withholding to diflerent degrees fromsaid signal-translating circuit the eflects of both sets ofoscillations, and varying the amplitude of said impressed current to amagnitude more closely approaching the amplitude of said sustainedoscillations than the amplitude of said decadent oscillations.

26. Radio receiving apparatus for distinguishing between oscillations ofradio frequency representing a desired signal and oscillationsrepresenting a disturbing eflect, comprising signal-translating meansinfluenced by both sets of oscillations, a control path includingcapacitative and inductive reactances and so disposed that changes inthe reactance of said path cause said sets of oscillations to influencesaid signal-translating means to different degrees, and means forchanging the reactance of said control path 27; Radio receivingapparatus for distinguishingbetween oscillations of radio frequencyrepresenting a desired signal and oscillations representing a disturbingeffect, comprising signal-translating means influencedvby both sets ofoscillations, a control path including capacitative and inductivereactances and so disposed'that changes in the reactance of said pathcause said sets of oscillations to influence said signal-translatingmeans to different degrees, and means for periodically changing thereactance of said control path.

28. Radio receiving apparatus for distinguishing between oscillations ofradio frequency representing a desired signal and oscillationsrepresenting a disturbing eflect, comprising signal-translating meansinfluenced by both sets of oscillations, a control path includingcapacitative and inductive reactances and so disposed that changes in.

the reactance of said path cause said sets of oscillations to influencesaid signal-translating means to different degrees, and means forimpressing upon said control path a periodic current for changing itsreactance.

29. Radio receiving apparatus for distinguishing between oscillations ofradio frequency representing a desired signal and oscillationsrepresenting a disturbing effect, comprising signal-translating meansinfluenced by both sets of oscillations, a control path includingcapacitative and inductive reactances and so disposed that changes inthe reactance of said path cause said sets of oscillations to influencesaid signal-translating means to different degrees, and means forimpressing upon said control path a periodic current of differentfrequency for periodically varying its reactness.

In testimony whereof I have hereunto affixed my signature this 13th dayof November, 1922.

DAVID Gr. MCGAA.

